Oxidation products of 6-substituted-2, 2, 4-trialkyl dihydroquinolines



United States Patent OXIDATION PRODUCTS OF 6-SUBSTITUTED-2,2,4 TRIALKYL DIHYDROQUINOLINES Frederick J. Webb, Cuyahoga Falls, Ohio, assignor to The Firestone Tire- & Rubber Company, Akron, Ohio, a corporation of Ohio NoDrawing. Application July 29,1955

Serial No. 525,361

6 Claims. (Cl. 260-288) This invention relates to the oxidation products of 6-substituted-2,2,4-trialkyl dihydroquinolines.

The 6 substituted 2,2,4'-trialkyl-1,2-dihydr0quinolines are commercially available. The-three alkyl substituents are methyl or ethyl or a mixture of the two. The 6-substituents are alkyl, aryl, alkoxy, or aryloxy. The alkyl of such substituen'ts may include 1 to 12 carbon atoms and the aryl may be phenyl or phenyl substituted with one or more alkyl suubstituents of 1 to 12 carbon atoms.

On oxidation, the two nitrogen groups are united. The oxidation compound is a hydrazine-type material of the following formula:

in which R, R and R" are alkyl substituents of the class consisting of methyl and ethyl and R is from the group consisting of alkyl, aryl, alkoxy, and aryloxy, as described.

The compounds are made by oxidation of the corresponding dihydroquinolines. The dihydroquinolines in which all three alkyl substituents are methyl, and those in which the two attached to the Z-carbon are methyl, and the third, attached to the 4-carbon is ethyl, are commercial, as in 2,2,4-trimethyl-6-ethoxy-1,2-dihydroquinoline and 2,2,4-trimethyl 6 phenyl-1,2-dihydroquinoline, etc. When two different dihydroquinolines are oxidized simultaneously, the substituents in the diflerent nuclei of the reaction product will be different.

The following examples represent the oxidation of the quinoline compounds:

EXAMPLE I A solution of 25 g. of 2,2,4-trimethyl-6-phenyl-1,2-dihydroquinoline in 400 ml. of permanganate-stable acetone was treated with 11.5 g. of potassium permanganate during a 3.5 hour period at 3 C. The mixture was filtered and the acetone allowed to evaporate at room temperature. The solid residue weighed 14.2 g. A five-gram portion was extracted ten times with ethyl alcoholat -50 C. and three times with petroleum ether and then air dried togive 3 g. of a white crystalline solid melting at 121-122" C. r j

Analysis.-Calcd. for C H N C, 87.07; H, 7.31; molecular weight, 497. Found: C, 86.75, 86.55; H, 7.25, 7.30; molecular weight, 522.

EXAMPLE II p A solution of 20.3 g. 0.1 'mole)- of' freshly distilled 2, 49,452 Patented Aug. 26, 1 958 2,2,4 trimethyl-6-ethoxy-1,2-dihydroquinoline in 400 ml. of permanganate-stable acetone, was cooled to 3 C. and treated gradually while stirring with 9.5 g. (0.06 mole) of potassium permanganate. Decolorization of the permanganate was very rapid. Later 3 g. potassium permanganate were added in one-gram lots. colorized rapidly. The mixture was filtered and the acetone evaporated at room temperature. was a dark brown, viscous oil.

Attempts were made to crystallize this material by dissolving it in petroleum ether and cooling in Dry-Ice alcohol. A gummy brown material separated. The supernatant liquid was poured 01f.

From this solution, on standing and partial evaporation, a crystalline solid separated; weight 5.0 g. After one washing with alcohol and one recrystallization from benzene and alcohol, the material melted at 109110 C.

Analysis-Calcd. for C H O N C, 77.73; H, 8.39; molecular weight 432.6. Found: C, 78.01, 78.10; H, 8.20, 8.11; molecular weight 425, 422.

Instead of the foregoing starting materials, other 2,2,4- trialkyl-6-substituted-1,Z-dihydroquinolines which may be used to produce the corresponding oxidation products which, in turn, are suitable for use as rubber antioxidants follow:

2,2,4-trimethyl-6-methoxy-1,2-dihydroquinoline 2,2,4-trimethyl-6-butoxy-1,Z-dihydroquinoline 2,2,4-triethyl-6-octoxy-1,Z-dihydroquinoline 2,Z-dimethyl-4-ethy1-6-undecoxy-1,Z-dihydroquinoline The rubber compositions in which the stabilizers may be used in small amounts include those used in tires, inner tubes, rubber threads, foamed rubber products, and other products from natural rubber or a sulfur-vulcanizable synthetic rubber polymer of butadiene or an alkyl derivative thereof, or rubber copolymer of butadiene or an alkyl derivative thereof with a vinyl cornonomer or a mixture of any of these rubbers or any similarly vulcanizable rubber composition.

By sulfur vulcanization is meant the curing of rubber by reaction with either free sulfur or a vulcanizing agent of the sulfur-donor type. Known agents of the latter type include the various phenol polysulfides, including the alkyl derivatives thereof, the xanthogen polysufides, the thiuram disulfides and polysulfides, various amine sulfides, including dialkylamine polysulfides and reaction products of primary amines with excess sulfur. Known vulcanization accelerators are useful in speeding up the vulcanization process and are operative herein, especially the relatively active accelerators, including the thiazole sulfenamides, 'e. g., cyclohexyl benzothiazole sulfenamide, thiazoline sulfenamides, thiocarbamyl sulfenamides, mercaptothiazoles, mercaptothiazolines, thiazolyl monoand This also de- The residue disulfides, the dithiocarbamates, the thiuram sulfides, xanthogen sulfides, metallic salts of mercaptothiazoles, mercaptothiazolines and dithiocarbamic acids. One or more accelerator activator. is often. used with any of the accelerators mentioned, and such activators include the various derivatives of guanidine known in the art, amine salts or organic and inorganic acids, various amines themselves, alkaline salts such as sodium acetate and the like, as well as other activators known to the art.

Additionally, two or more accelerators or accelerator combinations are sometimes desirable in a single rubber compound. Many of the accelerators mentioned above are suitable in latex formulations, especially such common accelerators as piperidinium pentamethylene dithiocarbamate, zinc butyl xanthate, zinc ethyl xanthate, zinc salt of mercaptobenzolthiazole, zinc dimethyl dithiocaroamate, zinc dibutyl dithiocarbarnate. Although vulcanization is usually accomplished by heating a vnlcanizable rubber composition at a temperature in the range of 240 to 400 F. for a time ranging from several hours to a few seconds, vulcanization does take place at lower temperatures, such as ordinary room temperature. It is quite common to vulcanize a latex film containing an ultraaccelerator by allowing the film to remain at room temperature for several hours or a few days.

The antioxidants of Examples I and II were compounded with rubber according to the following formula for a tread stock:

Natural rubber 100 Oil softener Stearic acid Zinc oxide Accelerator Sulfur Carbon black Antioxidant The various samples were cured 40 minutes at 280 F. The test properties of the cured samples are recorded in the following table, and these properties are compared with a blank similarly compounded but including no antioxidant. In the tables, modulus, tensile strength, and elongation are recorded in pounds per square inch. Oxygen absorption by the various samples was deter mined as described in the article by I. R. Shelton and Hugh Winn in Industrial and Engineering Chemistry, volume 38, page 71 (1948). By plotting the milliliters of oxygen absorbed per gram of rubber polymer, against the hours required for the absorption, and determining the slope of the straight-line portion of each curve which refers to the constant rate of oxygen absorption, the rates of absorption were obtained and are given in the tables.

Table 1 Formulation:

Masterbatch Blank Elongation 50 490 Properties after aging 2 days (air oven) at 212 F.:

Modulus (300%) 2,025 2, 125 Tensile 2, 025 2, 425 Tensile retained. 55 61 Elongation A. 315 3 Oxygen absorption, 90 0.:

Hours for absorption, 10 ml./g. rubber 19. 5 30 Total hours in absorption apparatus 32 55 Total oxygen absorbed, ml./g. rubber 15.8 20. 2 Rate of oxygen absorption, ml./hr./g 0. 380 0. 252 Properties after oxygen absorption:

Modulus (300%) Tensile a 575 1, 050 Elongation 180 250 A sample was prepared according to the same tread stock formula with one part of the oxidation product of Example II, and compared with a typical blank. The results are recorded below:

Table 2 Formulation:

Masterbatoh. 164 164 Blank (typical) Example 2 Normal pro pertics:

Modulus 300% 2,025 Modulus 400% 3, 200 Tensile 3, 775 Elongation 465 Oxygen absorption 0.:

Hrs. for absorption, 10 ml./g. rubber 19. 5 27 Hrs. for absorption, 20 ml./g. rubber. 44 Total hrs. in absorption apparatus. 32 45 Total oxygen absorbed/g. rubber 15.8 22. 6 Rate of oxygen absorption, ml./hr./g 0.380 0. 246 Properties after oxygen absorption:

Tensile 575 1, 225 Elongation 240 The results of the foregoing tests, as reported in both tables, show the compounds of this invention have a decided stabilizing effect, and produce improved vulcanizates.

The invention is defined by the claims which follow.

What I claim is:

1. As a new compound:

in which R, R and R" are alkyl substituents of the class consisting of methyl and ethyl and R' is from the group consisting of alkyl, aryl, alkoxy and aryloxy; the alkyl groups of the foregoing substituents each containing 1 to 12 carbon atoms, and the aryl groups being from the class consisting of phenyl and phenyl substituted with at least one alkyl substituent of 1 to 12 carbon atoms.

2. The compound of claim 1 in which the three alkyl groups of each nucleus are methyl.

3. The compound of claim 1 in which the R' groups are both phenyl.

4. The compound of claim 1 in which the R' groups are both ethoxy.

5. The compound of claim 1 in which the three alkyl groups of each nucleus are methyl and the two R' groups are phenyl.

6. The compound of claim 1 in which the three alkyl groups of each nucleus are methyl and the two R' groups are ethoxy.

References Cited in the file of this patent UNITED STATES PATENTS 2,208,216 Johnson et al. July 16, 1940 2,396,555 Cox Mar. 12, 1946 2,502,264 Lutz et al. Mar. 28, 1950 2,530,774 Kehe et al. Nov. 21, 1950 2,666,059 Davis Jan. 12, 1954 OTHER REFERENCES Elderfield: Heterocyclic Compounds, vol. 4, Wiley, New York, N. Y., 1952, page 317. 

1. AS NEW COMPOUND: 